TABLE 6.

cydA sequence changes observed in suppressor isolates^a

Suppressor isolate	Cotransduction frequency	Base change	Base position	Amino acid position	Amino acid change
PS1	0
PS3	0.89	C→T	770934	85	Ser→Phe
1A		None
1B	0.96	G→A	771129	150	Trp→stop
1C	0.83	None
1D	0.79	C→T	770934	85	Ser→Phe
1E	0.75	None
1F		G→A	771295	205	Trp→stop
1G	0.91	None
1H	0.85	None
1I	0.79	C→T	771003	108	Ser→Phe
1K	0.83
1L		G→A	771392	238	Gly→Ser
1M	0.88	None
1Nb	0.79	C→T	771402	241	Ser→Phe
1Nb		C→T	771477	266	Pro→Leu
1O	0.79	None
1P	0.96	None
1Q	0.95	None
1R	0.78	G→T	770888	70	Gly→Cys
1S	0.87	C→T	771668	330	Gln→stop
1Z	0.85	G→A	771460	261	Trp→stop
2A	0.84	G→A	771460	261	Trp→stop
2B	0	None
2E	0.85	None
2F	0.94	G→A	771395	240	Asp→Asn
2J	0.79	G→A	771392	239	Gly→Ser
2K	0.8	None
2N	0.93	G→A	770922	82	Trp→stop
2Q	0.65	G→A	771788	371	Ala→Thr

^aSequences were determined for the cydA gene from E. coli nucleotides 770738 to 772249 by using PCR products and primers described in Table 2 and sequencing in both directions. The cydA gene runs from nucleotide 770678 to nucleotide 772249. The cotransduction frequency is the fraction of replacements of cydA by cydA⁺ in a cross with phage P1 grown on a cydA⁺ nadA57::Tn10 strain. Frequencies were determined from 96 isolates screened as described in Materials and Methods. The nucleotide positions are the positions in the sequence published by Blattner et al. (6). The amino acid positions are the positions in the protein rather than the positions calculated from the gene sequence since the first ATG does not appear in the protein.

^bTwo base changes were found in the cydA region of this isolate.